1. Field of the Invention
The present invention relates to an original scanning apparatus for use, for example, in an image forming apparatus, such as an electronic copying machine containing an image forming means for forming an image corresponding to an original set on an original placing platen. More particularly the present invention relates to an original scanning apparatus having an automatic original feeding function for automatically conveying an original onto an original placing platen.
In a conventional image forming apparatus having an automatic original feeder, the automatic original feeder contains a wide endless conveying belt and a belt driving mechanism for rotatably feeding the conveying belt. The conveying belt and belt driving mechanism are disposed in a cover portion to be superposed on an original placing platen to transport an original from an original feeder provided at one end of the original placing platen onto the original placing platen and to exhaust the original. The original fed from the original feeder is set with a scale disposed at an opposite side to the original feeder, i.e., at the other end of the original placing platen as a reference.
Since the conventional automatic original feeder has, however, a wide conveying belt driving mechanism in the cover portion, the following problems arise.
The cost of the cover portion is high. The weight of the cover portion becomes heavy, and, as a result, the cover is rarely opened or closed. Since the wide conveying belt is rotatably fed in contact with all of the surface of the original placing platen, a large amount of power and a large power source are required. Also, noise is generated. Originals of A4 size are only about one-half the length of the original placing platen. When automatically fed, they are conveyed substantially the same distance as the length of the original placing platen. Thus, the original supplying cycle, in the case that a number of A4 originals are automatically fed, is increased and image forming efficiency is reduced.